Sanding or rubbing machine



March 2, 1948. A. c. BURLEIGH SANDING OR RUBBING MACHJiNE Filed May 2, 1945 2 Sheets-Sheet l 2 my mm M 1 0 Patented Mar. 2, 1948 1 OFFICE SANDING R RUBBING MACHINE Arthur C. Burleigh, Wellesley, Mass. Application May 2, 1945, Serial No. 591,457 I This invention relates to portable sanding machines of the type in which the sanding pad assembly, including the sanding pad, is given a rapid gyratory motion.

In machines of this type such rapid gyratory motion generates considerable vibration which, if not neutralized, is conveyed to the hands of the operator using the tool, thus causing more or less discomfort and rendering the sanding operation more or less difl'icult.

It is one of the objects of my present invention to provide a portable sanding machine of the above type with novel means forneutralizing or cancelling out the vibrations caused by the rapid gyratory motion of the sandingpad assembly.

Other objects of the invention are to provide various other improvements in portable sanding machines which will be more fully hereinafter set forth and then pointed out in the claims.

In the drawings wherein I have illustrated a selected embodiment of my invention,

Fig. 1 is a view partly in vertical section illustrating a sanding machine embodying the invention.

Fig. 2 is a section on the line 2-2, Fig. 1.

Fig. 3 is a section on the line 33, Fig. 1.

Fig. 4 is a section on the line 4-4, Fig. 1' showing the pad-locking lever in its inoperative position.

Fig. 5 is a section similar to Fig. 4 but showing the locking lever in its operative position.

Fig. 6 is a fragmentary perspective View showing the collar on the pad element which is secured to the supporting stud.

Fig. 7 is a fragmentary perspective View of the supporting stud.

The device herein illustrated comprises a head element I which is shown as being provided with a handle 2 by which it can be manipulated.

Suitably mounted in the head i are two vertical drive shafts 3 and 4, each shaft being mounted in suitable ball bearings 5.

Each shaft is formed at its lower end with two crank or eccentric portions 6 and l, the crank portion 6 of each shaft constituting an upper crank portion and the crank portion 1 constituting a lower crank portion. These crank portions are situated 180 apart and preferably they have the same throw. v

A sanding or rubbing pad assembly, including a pad 8 having either an abrasive or rubbing surface 8a, is mounted on the upper crank portions 6 of the two shafts, and a counterweight indicated generally at 9 is mounted on the lower'crank portions 1 of said two shafts.

4 Claims. (Cl. 51-170) The pad assembly comprises a drive plate l0 having two ball bearing assemblies II that are mounted on the crank portions 6 of the two drive shafts 3 and 4, said drive plate l0 being formed with a depending skirt or flange l2,'a supporting plate l3 secured to the lower edge of said flange, and the pad element 8 detachably secured to this supporting plate I3 by means which will be presently described.

The drive plate 10, its depending skirt l2 and the plate 13 constitute a housing member indicated generally at l5, within which the counter weight 9 is received. Said counterweight is provided with two ball bearing assemblies I4 which are mounted on the lower crank portions 1 of the two crank shafts.

Means are provided for rotating the two shafts 3 and 4 in unison, and for this purpose each shaft has a gear 16 mounted thereon which meshes with and is driven by a pinion I! on the shaft ll! of the motor l9 that is enclosed in the head I.

With this arrangement the synchronous rotation of the two drive shafts 3 and 4 will operate through the crank portions 6 to give the housing member 15 and the pad element 8 supported thereby a rapid gyratory motion. 7 Similarly the counterweight 9 will be given a rapid gyratory motion because it is mounted on the two crank portions 1 of the drive shafts 3 and 4. Inasmuch as the crank portions Band I of each shaft are situated apart; it will follow that the two gyratory motions of the sanding pad assembly and the counterweight'will be 180 out of phase. a result although the orbital motions of the pad assembly andthec'ounterweight are in the same direction, yet at any given instant, the direction of motion of the pad assembly in a linetangential to its orbital path is always opposite to that of the counterweight. Any vibration'caused by the gyratory motion of each gyrating element will, therefore, tend to neutralize and cancel out the vibration caused by the gyratory motion of the other gyratory element. By using a counterweight 9 having a, proper mass, said counterweight will completely neutralize or balance out any vibration caused by the gyratoi'y motion of the sanding pad assembly, and therefore, the machine will operate steadily and without any appreciable vibration. In the construction shown the bearings 5 not only constituteanti-iriction bearings for the shafts 6 and! but they also con-- stitute thrust bearings which take the. end thrust on said shafts resulting from the pressure applied tothe pad' during usego'f the implement.

It will be noted thatthe counterweight 9 is located within the housing member i 5. An advantage of this construction is that it makes it possible to place the counterweight relatively near the center of the gravity of the pad assembly, a construction which is conducive to still further neutralizing the vibrations caused by the gyratory motion of said pad assembly.

The means for detachably mounting the sanding pad element 8 on the housing member comprises a stud 20 which is secured to and depends from a plate '24 that is attached to the underside of the plate l3 of the housing member. The upper end 22 of this stud 20 is cylindrical, and the lower end 23 thereof is flat sided or square, and it is slightly larger than the cylindrical portion 2'2 of the stud. The sanding pad element is provided on its upper side with a collar v24 which has a square opening 3| therein that fits the square portion 23 of the stud 20. Said collar 24 is formed with a recess 25 in its upper face which receives a head portion 26 of a locking lever 27. The head 2.6 of the locking lever is provided with a square opening 28 of a size to fit the square end 23 of the stud 20. The head '26 of the said locking lever is retained in the recess 25 by a hold-down plate 29 that is screwed to the upper face of the collar 24. The collar 24 .is cut away on one side as indicated at 30 to provide an opening through which the lever 21 extends. This opening permits the locking lever 2-! to be turned from its inoperative position shown in .Fig. 4 .in which the square opening .28 therein registers with the square opening 3| in the collar 24 .to its operative position shown in Fig. in which the square opening of the head .2] is :out of register with the square opening in the collar.

In order to attach the sanding pad element to the housing, .the locking lever .21 will be turned into the position shown in Fig. 4, thereby bringing its square opening into register with the square opening 31 of the collar. The sanding pad element is then assembled with the housing by entering the square end '23 of the stud 20 through the square opening 28 .of the locking lever 21 and into the square opening 3| of the collar 24. When this has been done, the head 26 .of the lever 21 will be located just above the square portion 23 of the stud 20 and by turning the locking lever from its open position, shown in Fig. 4, to its operative position .shown in Fig. 5, the sides of the opening 28 of said lever will be carried across the corners of the square portion 23 of the stud, thereby locking the sanding pad element onto thestud.

The engagement of the square end 23 of the stud in the square opening of the collar 24 serves to hold the sanding pad from turning movement and thus rigidly connects it to the housing.

Th removal of thesanding pad :can be accomplished by simply swinging the locking lever from its operative position shown in Fig. 5 to its inoperative or open position shown in Fig. 4, and when this has been done, the sanding pad element is free to be withdrawn from the stud.

The sanding pad element may be provided with any usual means for clamping a facing 8a of sandpaper or of any other rubbing material to the underside thereof. Such means is shown as two clamping slides 40, each having at its outer end a clamping jaw '4! by which the ends of the facing 8a is clamped to the pad body. The inner end of each slide is bent upwardly as indicated at 42 and the two upturned portions 42 are connected by springs 43 which hold the clamping jaws in clamping position.

Mounted for turning movement on the collar 24 is a cam member 44 (shown in dotted lines) which engages the upturned portions 42 and is provided with a handle 45 by which it may be turned. When the cam is turned, it acts on the upturned flanges 42 and forces them apart, thus releasing the clamping pressure of the clamping jaws 4| so that the facing 8a can be removed or applied to the pad body. When the handle 45 and cam 44 are in the position shown in the drawings, the springs 43 will yieldingly hold the clamping jaws 4| in their operative position.

I will preferably make the supporting plate l3 of insulating material so as to insulate the pad from the head I, thereby obviating danger oi. any leakage of current from the motor circuit to the work.

Although I have referred to the machine as a sanding machine and to the pad element as a sanding pad, yet I wish to state that the invention is not limited to a machine in which the facing 8a has an abrasive action, but is equally applicable to a machine in which the facing 8a is one which has a rubbing or polishing action. In other words, the invention is in no way dependent on the character of the facing 8a. The terms sanding machine and sanding pad are, therefore, used in a generic sense as including any machine having the construction shown regardless of the character of the facing M.

I claim:

1. A portable sanding machine comprising a supporting head, a pair of drive shafts mounted therein, each drive shaft having two crank p or tions situated apart, a pad-carrying element mounted on one crank portion of each drive shaft, a sanding pad element secured to the pad-carrying element, a counterweight mounted on the other two crank portions of said drive shafts, and means to rotate said shafts, whereby both the pad-carrying element and the counterweight are given gyratory motions which are 180 out of phase with each other.

2. A portable sanding machine comprising a supporting head, a pair of drive shafts mounted therein, each drive shaft having two crank portions of equal throw but situated 180 apart, a pad-carrying element mounted on one crank portion of each drive shaft, a sanding pad carried by said pad-carrying element, a counterweight mounted on the other two crank portions of said drive shafts, and means to rotate said shafts.

3. A portable sanding machine comprising a supporting head, a pair of vertical drive shafts mounted therein, each drive shaft having an upper crank portion and a lower crank portion, the two crank portions of each shaft being 180 apart, a housing member mounted on the two upper crank portions, a sanding pad secured to the housing member, a counterweight situated within the housing and mounted on the two lower crank portions of the drive shafts, and means to rotate the shafts.

4. A machine of the class described comprising a head element, a motor mounted therein, a pad assembly including a drive plate, a supporting plate of insulating, material rigidlysecured to the under side of the drive plate and a pad element rigidly secured to the supporting plate, the drive plate, the supporting plate and the pad element thus being rigidly connected to move together as a unit and means operated by the motor to give the pad assembly a vibrating motion, said supporting plate of insulating material 5 6 serving both to support the pad element and. to UNITED STATES PATENTS insulate it from the other operative parts.

ARTHUR c. BURLEIGH. Number m Date 1,785,695 Ekstrom Dec. 16, 1930 REFERENCES CITED 5 1,924,575 Pearson Apr. 10, 1934 1,9 7,790 Mavis et a1. May 8, 1934 The following references are of record in the 2,276,534 Burleigh Man 17, 1942 file this patent 2,395,537 Crosby Feb. 26, 1946 

